PROBLEM SUMMARY: Decoders with "BEMF" motor control will have problems operating correctly on any Bachmann engine even if the engine offers a plug and play DCC socket for a DCC decoder. Many people may falsely assume there is something wrong with the decoder and blame the decoder because when they put in a different decoder it works. This is unfortunate. The problem is a two capacitors that Bachmann installs on all of it engines that is causing the problem. The solution is to remove the two capacitors. If you wish to learn a lot more about this problem in general terms, go here: Motor Capacitors
NO WARRANTY VIOLATION. BACHMANN SAY'S ITS OK TO REMOVE THE CAPACITORS
Bachmann acknowledges the problem as being caused by their circuit and the solution is discussed on Bachmann's Website in their FAQ page IF you dig deep enough.You can find it here on the UK website in the section titled: Open chassis diesel
http://www.bachmann.co.uk/service/dcc2.php
Below was from the ORIGINAL webpage on the Bachmann US website. Bachmann has since changed it's website such that the link to it no longer works.
------------------------------------------
The Bachmann Website says (picture included):
"Why does Bachmann put capacitors and chokes in its locomotives and must I remove them to use with DCC?
Bachmann sells its model railroad locomotives worldwide. Many countries require very strict electronic emission controls. In order to meet these controls we are required to install suppression capacitors and inductors on our locomotives. Most DCC decoders (including Bachmann E-Z Command decoders) can work properly with these components installed. If you want to install a decoder that requires removal of these components, Bachmann will continue to warrant the locomotive so long as the locomotive is used in the US or Canada."
The capacitors can be removed without effecting operation. If you remove the inductors you will have to install a wire in its place."
------------------------------------
WHERE ARE THE CAPACITORS?
This is the big problem because they may not be easy to find.
They can be found directly on the motor or on a PCB board found inside the locomotive that feeds power to the motor. The PCB board varys in physical form factor depending on the unique needs and space that can be found inside the engine. Further more the package technology has also changed with the age of the engine. Older engines used through hole parts while the lasted engines use Surface Mount Technology (SMT).
Some manuals have instructions about where they are and/or asking them to be removed.
http://www.soundtraxx.com/documents/appnotes/bachmann_gp9.pdf
http://www.tcsdcc.com/Customer_Content/Technical_Info/Tech_Info/FAQPage.php?q=16
http://www.digitrax.com/tsd/KB538/capacitors-in-bachmanns-spectrum-steam-locos/
9/9/15